1 /*
2 * Copyright (c) 2013, 2020, Oracle and/or its affiliates. All rights reserved.
3 * Copyright (c) 2019, Azul Systems, Inc. All rights reserved.
4 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
5 *
6 * This code is free software; you can redistribute it and/or modify it
7 * under the terms of the GNU General Public License version 2 only, as
8 * published by the Free Software Foundation. Oracle designates this
9 * particular file as subject to the "Classpath" exception as provided
10 * by Oracle in the LICENSE file that accompanied this code.
11 *
12 * This code is distributed in the hope that it will be useful, but WITHOUT
13 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
14 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
15 * version 2 for more details (a copy is included in the LICENSE file that
16 * accompanied this code).
17 *
18 * You should have received a copy of the GNU General Public License version
19 * 2 along with this work; if not, write to the Free Software Foundation,
20 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
21 *
22 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
23 * or visit www.oracle.com if you need additional information or have any
24 * questions.
25 */
26
27 package java.lang;
28
29 import java.io.InputStream;
30 import java.io.IOException;
31 import java.io.UncheckedIOException;
32 import java.io.File;
33 import java.lang.reflect.Constructor;
34 import java.lang.reflect.InvocationTargetException;
35 import java.net.URL;
36 import java.security.AccessController;
37 import java.security.AccessControlContext;
38 import java.security.CodeSource;
39 import java.security.PrivilegedAction;
40 import java.security.ProtectionDomain;
41 import java.security.cert.Certificate;
42 import java.util.ArrayList;
43 import java.util.Collections;
44 import java.util.Enumeration;
45 import java.util.HashMap;
46 import java.util.Map;
47 import java.util.NoSuchElementException;
48 import java.util.Objects;
49 import java.util.Set;
50 import java.util.Spliterator;
51 import java.util.Spliterators;
52 import java.util.WeakHashMap;
53 import java.util.concurrent.ConcurrentHashMap;
54 import java.util.function.Supplier;
55 import java.util.stream.Stream;
56 import java.util.stream.StreamSupport;
57
58 import jdk.internal.loader.BootLoader;
59 import jdk.internal.loader.BuiltinClassLoader;
60 import jdk.internal.loader.ClassLoaders;
61 import jdk.internal.loader.NativeLibrary;
62 import jdk.internal.loader.NativeLibraries;
63 import jdk.internal.perf.PerfCounter;
64 import jdk.internal.misc.Unsafe;
65 import jdk.internal.misc.VM;
66 import jdk.internal.reflect.CallerSensitive;
67 import jdk.internal.reflect.Reflection;
68 import jdk.internal.util.StaticProperty;
69 import sun.reflect.misc.ReflectUtil;
70 import sun.security.util.SecurityConstants;
71
72 /**
73 * A class loader is an object that is responsible for loading classes. The
74 * class {@code ClassLoader} is an abstract class. Given the <a
75 * href="#binary-name">binary name</a> of a class, a class loader should attempt to
76 * locate or generate data that constitutes a definition for the class. A
77 * typical strategy is to transform the name into a file name and then read a
78 * "class file" of that name from a file system.
79 *
80 * <p> Every {@link java.lang.Class Class} object contains a {@link
81 * Class#getClassLoader() reference} to the {@code ClassLoader} that defined
82 * it.
83 *
84 * <p> {@code Class} objects for array classes are not created by class
85 * loaders, but are created automatically as required by the Java runtime.
86 * The class loader for an array class, as returned by {@link
87 * Class#getClassLoader()} is the same as the class loader for its element
88 * type; if the element type is a primitive type, then the array class has no
89 * class loader.
90 *
91 * <p> Applications implement subclasses of {@code ClassLoader} in order to
92 * extend the manner in which the Java virtual machine dynamically loads
93 * classes.
94 *
95 * <p> Class loaders may typically be used by security managers to indicate
96 * security domains.
97 *
98 * <p> In addition to loading classes, a class loader is also responsible for
99 * locating resources. A resource is some data (a "{@code .class}" file,
100 * configuration data, or an image for example) that is identified with an
101 * abstract '/'-separated path name. Resources are typically packaged with an
102 * application or library so that they can be located by code in the
103 * application or library. In some cases, the resources are included so that
104 * they can be located by other libraries.
105 *
106 * <p> The {@code ClassLoader} class uses a delegation model to search for
107 * classes and resources. Each instance of {@code ClassLoader} has an
108 * associated parent class loader. When requested to find a class or
109 * resource, a {@code ClassLoader} instance will usually delegate the search
110 * for the class or resource to its parent class loader before attempting to
111 * find the class or resource itself.
112 *
113 * <p> Class loaders that support concurrent loading of classes are known as
114 * <em>{@linkplain #isRegisteredAsParallelCapable() parallel capable}</em> class
115 * loaders and are required to register themselves at their class initialization
116 * time by invoking the {@link
117 * #registerAsParallelCapable ClassLoader.registerAsParallelCapable}
118 * method. Note that the {@code ClassLoader} class is registered as parallel
119 * capable by default. However, its subclasses still need to register themselves
120 * if they are parallel capable.
121 * In environments in which the delegation model is not strictly
122 * hierarchical, class loaders need to be parallel capable, otherwise class
123 * loading can lead to deadlocks because the loader lock is held for the
124 * duration of the class loading process (see {@link #loadClass
125 * loadClass} methods).
126 *
127 * <h2> <a id="builtinLoaders">Run-time Built-in Class Loaders</a></h2>
128 *
129 * The Java run-time has the following built-in class loaders:
130 *
131 * <ul>
132 * <li><p>Bootstrap class loader.
133 * It is the virtual machine's built-in class loader, typically represented
134 * as {@code null}, and does not have a parent.</li>
135 * <li><p>{@linkplain #getPlatformClassLoader() Platform class loader}.
136 * All <em>platform classes</em> are visible to the platform class loader
137 * that can be used as the parent of a {@code ClassLoader} instance.
138 * Platform classes include Java SE platform APIs, their implementation
139 * classes and JDK-specific run-time classes that are defined by the
140 * platform class loader or its ancestors.
141 * <p> To allow for upgrading/overriding of modules defined to the platform
142 * class loader, and where upgraded modules read modules defined to class
143 * loaders other than the platform class loader and its ancestors, then
144 * the platform class loader may have to delegate to other class loaders,
145 * the application class loader for example.
146 * In other words, classes in named modules defined to class loaders
147 * other than the platform class loader and its ancestors may be visible
148 * to the platform class loader. </li>
149 * <li><p>{@linkplain #getSystemClassLoader() System class loader}.
150 * It is also known as <em>application class loader</em> and is distinct
151 * from the platform class loader.
152 * The system class loader is typically used to define classes on the
153 * application class path, module path, and JDK-specific tools.
154 * The platform class loader is a parent or an ancestor of the system class
155 * loader that all platform classes are visible to it.</li>
156 * </ul>
157 *
158 * <p> Normally, the Java virtual machine loads classes from the local file
159 * system in a platform-dependent manner.
160 * However, some classes may not originate from a file; they may originate
161 * from other sources, such as the network, or they could be constructed by an
162 * application. The method {@link #defineClass(String, byte[], int, int)
163 * defineClass} converts an array of bytes into an instance of class
164 * {@code Class}. Instances of this newly defined class can be created using
165 * {@link Class#newInstance Class.newInstance}.
166 *
167 * <p> The methods and constructors of objects created by a class loader may
168 * reference other classes. To determine the class(es) referred to, the Java
169 * virtual machine invokes the {@link #loadClass loadClass} method of
170 * the class loader that originally created the class.
171 *
172 * <p> For example, an application could create a network class loader to
173 * download class files from a server. Sample code might look like:
174 *
175 * <blockquote><pre>
176 * ClassLoader loader = new NetworkClassLoader(host, port);
177 * Object main = loader.loadClass("Main", true).newInstance();
178 * . . .
179 * </pre></blockquote>
180 *
181 * <p> The network class loader subclass must define the methods {@link
182 * #findClass findClass} and {@code loadClassData} to load a class
183 * from the network. Once it has downloaded the bytes that make up the class,
184 * it should use the method {@link #defineClass defineClass} to
185 * create a class instance. A sample implementation is:
186 *
187 * <blockquote><pre>
188 * class NetworkClassLoader extends ClassLoader {
189 * String host;
190 * int port;
191 *
192 * public Class findClass(String name) {
193 * byte[] b = loadClassData(name);
194 * return defineClass(name, b, 0, b.length);
195 * }
196 *
197 * private byte[] loadClassData(String name) {
198 * // load the class data from the connection
199 * . . .
200 * }
201 * }
202 * </pre></blockquote>
203 *
204 * <h3> <a id="binary-name">Binary names</a> </h3>
205 *
206 * <p> Any class name provided as a {@code String} parameter to methods in
207 * {@code ClassLoader} must be a binary name as defined by
208 * <cite>The Java™ Language Specification</cite>.
209 *
210 * <p> Examples of valid class names include:
211 * <blockquote><pre>
212 * "java.lang.String"
213 * "javax.swing.JSpinner$DefaultEditor"
214 * "java.security.KeyStore$Builder$FileBuilder$1"
215 * "java.net.URLClassLoader$3$1"
216 * </pre></blockquote>
217 *
218 * <p> Any package name provided as a {@code String} parameter to methods in
219 * {@code ClassLoader} must be either the empty string (denoting an unnamed package)
220 * or a fully qualified name as defined by
221 * <cite>The Java™ Language Specification</cite>.
222 *
223 * @jls 6.7 Fully Qualified Names
224 * @jls 13.1 The Form of a Binary
225 * @see #resolveClass(Class)
226 * @since 1.0
227 * @revised 9
228 * @spec JPMS
229 */
230 public abstract class ClassLoader {
231
232 private static native void registerNatives();
233 static {
234 registerNatives();
235 }
236
237 // The parent class loader for delegation
238 // Note: VM hardcoded the offset of this field, thus all new fields
239 // must be added *after* it.
240 private final ClassLoader parent;
241
242 // class loader name
243 private final String name;
244
245 // the unnamed module for this ClassLoader
246 private final Module unnamedModule;
247
248 // a string for exception message printing
249 private final String nameAndId;
250
251 /**
252 * Encapsulates the set of parallel capable loader types.
253 */
254 private static class ParallelLoaders {
255 private ParallelLoaders() {}
256
257 // the set of parallel capable loader types
258 private static final Set<Class<? extends ClassLoader>> loaderTypes =
259 Collections.newSetFromMap(new WeakHashMap<>());
260 static {
261 synchronized (loaderTypes) { loaderTypes.add(ClassLoader.class); }
262 }
263
264 /**
265 * Registers the given class loader type as parallel capable.
266 * Returns {@code true} is successfully registered; {@code false} if
267 * loader's super class is not registered.
268 */
269 static boolean register(Class<? extends ClassLoader> c) {
270 synchronized (loaderTypes) {
271 if (loaderTypes.contains(c.getSuperclass())) {
272 // register the class loader as parallel capable
273 // if and only if all of its super classes are.
274 // Note: given current classloading sequence, if
275 // the immediate super class is parallel capable,
276 // all the super classes higher up must be too.
277 loaderTypes.add(c);
278 return true;
279 } else {
280 return false;
281 }
282 }
283 }
284
285 /**
286 * Returns {@code true} if the given class loader type is
287 * registered as parallel capable.
288 */
289 static boolean isRegistered(Class<? extends ClassLoader> c) {
290 synchronized (loaderTypes) {
291 return loaderTypes.contains(c);
292 }
293 }
294 }
295
296 // Maps class name to the corresponding lock object when the current
297 // class loader is parallel capable.
298 // Note: VM also uses this field to decide if the current class loader
299 // is parallel capable and the appropriate lock object for class loading.
300 private final ConcurrentHashMap<String, Object> parallelLockMap;
301
302 // Maps packages to certs
303 private final ConcurrentHashMap<String, Certificate[]> package2certs;
304
305 // Shared among all packages with unsigned classes
306 private static final Certificate[] nocerts = new Certificate[0];
307
308 // The classes loaded by this class loader. The only purpose of this table
309 // is to keep the classes from being GC'ed until the loader is GC'ed.
310 private final ArrayList<Class<?>> classes = new ArrayList<>();
311
312 // The "default" domain. Set as the default ProtectionDomain on newly
313 // created classes.
314 private final ProtectionDomain defaultDomain =
315 new ProtectionDomain(new CodeSource(null, (Certificate[]) null),
316 null, this, null);
317
318 // Invoked by the VM to record every loaded class with this loader.
319 void addClass(Class<?> c) {
320 synchronized (classes) {
321 classes.add(c);
322 }
323 }
324
325 // The packages defined in this class loader. Each package name is
326 // mapped to its corresponding NamedPackage object.
327 //
328 // The value is a Package object if ClassLoader::definePackage,
329 // Class::getPackage, ClassLoader::getDefinePackage(s) or
330 // Package::getPackage(s) method is called to define it.
331 // Otherwise, the value is a NamedPackage object.
332 private final ConcurrentHashMap<String, NamedPackage> packages
333 = new ConcurrentHashMap<>();
334
335 /*
336 * Returns a named package for the given module.
337 */
338 private NamedPackage getNamedPackage(String pn, Module m) {
339 NamedPackage p = packages.get(pn);
340 if (p == null) {
341 p = new NamedPackage(pn, m);
342
343 NamedPackage value = packages.putIfAbsent(pn, p);
344 if (value != null) {
345 // Package object already be defined for the named package
346 p = value;
347 // if definePackage is called by this class loader to define
348 // a package in a named module, this will return Package
349 // object of the same name. Package object may contain
350 // unexpected information but it does not impact the runtime.
351 // this assertion may be helpful for troubleshooting
352 assert value.module() == m;
353 }
354 }
355 return p;
356 }
357
358 private static Void checkCreateClassLoader() {
359 return checkCreateClassLoader(null);
360 }
361
362 private static Void checkCreateClassLoader(String name) {
363 if (name != null && name.isEmpty()) {
364 throw new IllegalArgumentException("name must be non-empty or null");
365 }
366
367 SecurityManager security = System.getSecurityManager();
368 if (security != null) {
369 security.checkCreateClassLoader();
370 }
371 return null;
372 }
373
374 private ClassLoader(Void unused, String name, ClassLoader parent) {
375 this.name = name;
376 this.parent = parent;
377 this.unnamedModule = new Module(this);
378 if (ParallelLoaders.isRegistered(this.getClass())) {
379 parallelLockMap = new ConcurrentHashMap<>();
380 assertionLock = new Object();
381 } else {
382 // no finer-grained lock; lock on the classloader instance
383 parallelLockMap = null;
384 assertionLock = this;
385 }
386 this.package2certs = new ConcurrentHashMap<>();
387 this.nameAndId = nameAndId(this);
388 }
389
390 /**
391 * If the defining loader has a name explicitly set then
392 * '<loader-name>' @<id>
393 * If the defining loader has no name then
394 * <qualified-class-name> @<id>
395 * If it's built-in loader then omit `@<id>` as there is only one instance.
396 */
397 private static String nameAndId(ClassLoader ld) {
398 String nid = ld.getName() != null ? "\'" + ld.getName() + "\'"
399 : ld.getClass().getName();
400 if (!(ld instanceof BuiltinClassLoader)) {
401 String id = Integer.toHexString(System.identityHashCode(ld));
402 nid = nid + " @" + id;
403 }
404 return nid;
405 }
406
407 /**
408 * Creates a new class loader of the specified name and using the
409 * specified parent class loader for delegation.
410 *
411 * @apiNote If the parent is specified as {@code null} (for the
412 * bootstrap class loader) then there is no guarantee that all platform
413 * classes are visible.
414 *
415 * @param name class loader name; or {@code null} if not named
416 * @param parent the parent class loader
417 *
418 * @throws IllegalArgumentException if the given name is empty.
419 *
420 * @throws SecurityException
421 * If a security manager exists and its
422 * {@link SecurityManager#checkCreateClassLoader()}
423 * method doesn't allow creation of a new class loader.
424 *
425 * @since 9
426 * @spec JPMS
427 */
428 protected ClassLoader(String name, ClassLoader parent) {
429 this(checkCreateClassLoader(name), name, parent);
430 }
431
432 /**
433 * Creates a new class loader using the specified parent class loader for
434 * delegation.
435 *
436 * <p> If there is a security manager, its {@link
437 * SecurityManager#checkCreateClassLoader() checkCreateClassLoader} method
438 * is invoked. This may result in a security exception. </p>
439 *
440 * @apiNote If the parent is specified as {@code null} (for the
441 * bootstrap class loader) then there is no guarantee that all platform
442 * classes are visible.
443 *
444 * @param parent
445 * The parent class loader
446 *
447 * @throws SecurityException
448 * If a security manager exists and its
449 * {@code checkCreateClassLoader} method doesn't allow creation
450 * of a new class loader.
451 *
452 * @since 1.2
453 */
454 protected ClassLoader(ClassLoader parent) {
455 this(checkCreateClassLoader(), null, parent);
456 }
457
458 /**
459 * Creates a new class loader using the {@code ClassLoader} returned by
460 * the method {@link #getSystemClassLoader()
461 * getSystemClassLoader()} as the parent class loader.
462 *
463 * <p> If there is a security manager, its {@link
464 * SecurityManager#checkCreateClassLoader()
465 * checkCreateClassLoader} method is invoked. This may result in
466 * a security exception. </p>
467 *
468 * @throws SecurityException
469 * If a security manager exists and its
470 * {@code checkCreateClassLoader} method doesn't allow creation
471 * of a new class loader.
472 */
473 protected ClassLoader() {
474 this(checkCreateClassLoader(), null, getSystemClassLoader());
475 }
476
477 /**
478 * Returns the name of this class loader or {@code null} if
479 * this class loader is not named.
480 *
481 * @apiNote This method is non-final for compatibility. If this
482 * method is overridden, this method must return the same name
483 * as specified when this class loader was instantiated.
484 *
485 * @return name of this class loader; or {@code null} if
486 * this class loader is not named.
487 *
488 * @since 9
489 * @spec JPMS
490 */
491 public String getName() {
492 return name;
493 }
494
495 // package-private used by StackTraceElement to avoid
496 // calling the overrideable getName method
497 final String name() {
498 return name;
499 }
500
501 // -- Class --
502
503 /**
504 * Loads the class with the specified <a href="#binary-name">binary name</a>.
505 * This method searches for classes in the same manner as the {@link
506 * #loadClass(String, boolean)} method. It is invoked by the Java virtual
507 * machine to resolve class references. Invoking this method is equivalent
508 * to invoking {@link #loadClass(String, boolean) loadClass(name,
509 * false)}.
510 *
511 * @param name
512 * The <a href="#binary-name">binary name</a> of the class
513 *
514 * @return The resulting {@code Class} object
515 *
516 * @throws ClassNotFoundException
517 * If the class was not found
518 */
519 public Class<?> loadClass(String name) throws ClassNotFoundException {
520 return loadClass(name, false);
521 }
522
523 /**
524 * Loads the class with the specified <a href="#binary-name">binary name</a>. The
525 * default implementation of this method searches for classes in the
526 * following order:
527 *
528 * <ol>
529 *
530 * <li><p> Invoke {@link #findLoadedClass(String)} to check if the class
531 * has already been loaded. </p></li>
532 *
533 * <li><p> Invoke the {@link #loadClass(String) loadClass} method
534 * on the parent class loader. If the parent is {@code null} the class
535 * loader built into the virtual machine is used, instead. </p></li>
536 *
537 * <li><p> Invoke the {@link #findClass(String)} method to find the
538 * class. </p></li>
539 *
540 * </ol>
541 *
542 * <p> If the class was found using the above steps, and the
543 * {@code resolve} flag is true, this method will then invoke the {@link
544 * #resolveClass(Class)} method on the resulting {@code Class} object.
545 *
546 * <p> Subclasses of {@code ClassLoader} are encouraged to override {@link
547 * #findClass(String)}, rather than this method. </p>
548 *
549 * <p> Unless overridden, this method synchronizes on the result of
550 * {@link #getClassLoadingLock getClassLoadingLock} method
551 * during the entire class loading process.
552 *
553 * @param name
554 * The <a href="#binary-name">binary name</a> of the class
555 *
556 * @param resolve
557 * If {@code true} then resolve the class
558 *
559 * @return The resulting {@code Class} object
560 *
561 * @throws ClassNotFoundException
562 * If the class could not be found
563 */
564 protected Class<?> loadClass(String name, boolean resolve)
565 throws ClassNotFoundException
566 {
567 synchronized (getClassLoadingLock(name)) {
568 // First, check if the class has already been loaded
569 Class<?> c = findLoadedClass(name);
570 if (c == null) {
571 long t0 = System.nanoTime();
572 try {
573 if (parent != null) {
574 c = parent.loadClass(name, false);
575 } else {
576 c = findBootstrapClassOrNull(name);
577 }
578 } catch (ClassNotFoundException e) {
579 // ClassNotFoundException thrown if class not found
580 // from the non-null parent class loader
581 }
582
583 if (c == null) {
584 // If still not found, then invoke findClass in order
585 // to find the class.
586 long t1 = System.nanoTime();
587 c = findClass(name);
588
589 // this is the defining class loader; record the stats
590 PerfCounter.getParentDelegationTime().addTime(t1 - t0);
591 PerfCounter.getFindClassTime().addElapsedTimeFrom(t1);
592 PerfCounter.getFindClasses().increment();
593 }
594 }
595 if (resolve) {
596 resolveClass(c);
597 }
598 return c;
599 }
600 }
601
602 /**
603 * Loads the class with the specified <a href="#binary-name">binary name</a>
604 * in a module defined to this class loader. This method returns {@code null}
605 * if the class could not be found.
606 *
607 * @apiNote This method does not delegate to the parent class loader.
608 *
609 * @implSpec The default implementation of this method searches for classes
610 * in the following order:
611 *
612 * <ol>
613 * <li>Invoke {@link #findLoadedClass(String)} to check if the class
614 * has already been loaded.</li>
615 * <li>Invoke the {@link #findClass(String, String)} method to find the
616 * class in the given module.</li>
617 * </ol>
618 *
619 * @param module
620 * The module
621 * @param name
622 * The <a href="#binary-name">binary name</a> of the class
623 *
624 * @return The resulting {@code Class} object in a module defined by
625 * this class loader, or {@code null} if the class could not be found.
626 */
627 final Class<?> loadClass(Module module, String name) {
628 synchronized (getClassLoadingLock(name)) {
629 // First, check if the class has already been loaded
630 Class<?> c = findLoadedClass(name);
631 if (c == null) {
632 c = findClass(module.getName(), name);
633 }
634 if (c != null && c.getModule() == module) {
635 return c;
636 } else {
637 return null;
638 }
639 }
640 }
641
642 /**
643 * Returns the lock object for class loading operations.
644 * For backward compatibility, the default implementation of this method
645 * behaves as follows. If this ClassLoader object is registered as
646 * parallel capable, the method returns a dedicated object associated
647 * with the specified class name. Otherwise, the method returns this
648 * ClassLoader object.
649 *
650 * @param className
651 * The name of the to-be-loaded class
652 *
653 * @return the lock for class loading operations
654 *
655 * @throws NullPointerException
656 * If registered as parallel capable and {@code className} is null
657 *
658 * @see #loadClass(String, boolean)
659 *
660 * @since 1.7
661 */
662 protected Object getClassLoadingLock(String className) {
663 Object lock = this;
664 if (parallelLockMap != null) {
665 Object newLock = new Object();
666 lock = parallelLockMap.putIfAbsent(className, newLock);
667 if (lock == null) {
668 lock = newLock;
669 }
670 }
671 return lock;
672 }
673
674 // Invoked by the VM after loading class with this loader.
675 private void checkPackageAccess(Class<?> cls, ProtectionDomain pd) {
676 final SecurityManager sm = System.getSecurityManager();
677 if (sm != null) {
678 if (ReflectUtil.isNonPublicProxyClass(cls)) {
679 for (Class<?> intf: cls.getInterfaces()) {
680 checkPackageAccess(intf, pd);
681 }
682 return;
683 }
684
685 final String packageName = cls.getPackageName();
686 if (!packageName.isEmpty()) {
687 AccessController.doPrivileged(new PrivilegedAction<>() {
688 public Void run() {
689 sm.checkPackageAccess(packageName);
690 return null;
691 }
692 }, new AccessControlContext(new ProtectionDomain[] {pd}));
693 }
694 }
695 }
696
697 /**
698 * Finds the class with the specified <a href="#binary-name">binary name</a>.
699 * This method should be overridden by class loader implementations that
700 * follow the delegation model for loading classes, and will be invoked by
701 * the {@link #loadClass loadClass} method after checking the
702 * parent class loader for the requested class.
703 *
704 * @implSpec The default implementation throws {@code ClassNotFoundException}.
705 *
706 * @param name
707 * The <a href="#binary-name">binary name</a> of the class
708 *
709 * @return The resulting {@code Class} object
710 *
711 * @throws ClassNotFoundException
712 * If the class could not be found
713 *
714 * @since 1.2
715 */
716 protected Class<?> findClass(String name) throws ClassNotFoundException {
717 throw new ClassNotFoundException(name);
718 }
719
720 /**
721 * Finds the class with the given <a href="#binary-name">binary name</a>
722 * in a module defined to this class loader.
723 * Class loader implementations that support loading from modules
724 * should override this method.
725 *
726 * @apiNote This method returns {@code null} rather than throwing
727 * {@code ClassNotFoundException} if the class could not be found.
728 *
729 * @implSpec The default implementation attempts to find the class by
730 * invoking {@link #findClass(String)} when the {@code moduleName} is
731 * {@code null}. It otherwise returns {@code null}.
732 *
733 * @param moduleName
734 * The module name; or {@code null} to find the class in the
735 * {@linkplain #getUnnamedModule() unnamed module} for this
736 * class loader
737 * @param name
738 * The <a href="#binary-name">binary name</a> of the class
739 *
740 * @return The resulting {@code Class} object, or {@code null}
741 * if the class could not be found.
742 *
743 * @since 9
744 * @spec JPMS
745 */
746 protected Class<?> findClass(String moduleName, String name) {
747 if (moduleName == null) {
748 try {
749 return findClass(name);
750 } catch (ClassNotFoundException ignore) { }
751 }
752 return null;
753 }
754
755
756 /**
757 * Converts an array of bytes into an instance of class {@code Class}.
758 * Before the {@code Class} can be used it must be resolved. This method
759 * is deprecated in favor of the version that takes a <a
760 * href="#binary-name">binary name</a> as its first argument, and is more secure.
761 *
762 * @param b
763 * The bytes that make up the class data. The bytes in positions
764 * {@code off} through {@code off+len-1} should have the format
765 * of a valid class file as defined by
766 * <cite>The Java™ Virtual Machine Specification</cite>.
767 *
768 * @param off
769 * The start offset in {@code b} of the class data
770 *
771 * @param len
772 * The length of the class data
773 *
774 * @return The {@code Class} object that was created from the specified
775 * class data
776 *
777 * @throws ClassFormatError
778 * If the data did not contain a valid class
779 *
780 * @throws IndexOutOfBoundsException
781 * If either {@code off} or {@code len} is negative, or if
782 * {@code off+len} is greater than {@code b.length}.
783 *
784 * @throws SecurityException
785 * If an attempt is made to add this class to a package that
786 * contains classes that were signed by a different set of
787 * certificates than this class, or if an attempt is made
788 * to define a class in a package with a fully-qualified name
789 * that starts with "{@code java.}".
790 *
791 * @see #loadClass(String, boolean)
792 * @see #resolveClass(Class)
793 *
794 * @deprecated Replaced by {@link #defineClass(String, byte[], int, int)
795 * defineClass(String, byte[], int, int)}
796 */
797 @Deprecated(since="1.1")
798 protected final Class<?> defineClass(byte[] b, int off, int len)
799 throws ClassFormatError
800 {
801 return defineClass(null, b, off, len, null);
802 }
803
804 /**
805 * Converts an array of bytes into an instance of class {@code Class}.
806 * Before the {@code Class} can be used it must be resolved.
807 *
808 * <p> This method assigns a default {@link java.security.ProtectionDomain
809 * ProtectionDomain} to the newly defined class. The
810 * {@code ProtectionDomain} is effectively granted the same set of
811 * permissions returned when {@link
812 * java.security.Policy#getPermissions(java.security.CodeSource)
813 * Policy.getPolicy().getPermissions(new CodeSource(null, null))}
814 * is invoked. The default protection domain is created on the first invocation
815 * of {@link #defineClass(String, byte[], int, int) defineClass},
816 * and re-used on subsequent invocations.
817 *
818 * <p> To assign a specific {@code ProtectionDomain} to the class, use
819 * the {@link #defineClass(String, byte[], int, int,
820 * java.security.ProtectionDomain) defineClass} method that takes a
821 * {@code ProtectionDomain} as one of its arguments. </p>
822 *
823 * <p>
824 * This method defines a package in this class loader corresponding to the
825 * package of the {@code Class} (if such a package has not already been defined
826 * in this class loader). The name of the defined package is derived from
827 * the <a href="#binary-name">binary name</a> of the class specified by
828 * the byte array {@code b}.
829 * Other properties of the defined package are as specified by {@link Package}.
830 *
831 * @param name
832 * The expected <a href="#binary-name">binary name</a> of the class, or
833 * {@code null} if not known
834 *
835 * @param b
836 * The bytes that make up the class data. The bytes in positions
837 * {@code off} through {@code off+len-1} should have the format
838 * of a valid class file as defined by
839 * <cite>The Java™ Virtual Machine Specification</cite>.
840 *
841 * @param off
842 * The start offset in {@code b} of the class data
843 *
844 * @param len
845 * The length of the class data
846 *
847 * @return The {@code Class} object that was created from the specified
848 * class data.
849 *
850 * @throws ClassFormatError
851 * If the data did not contain a valid class
852 *
853 * @throws IndexOutOfBoundsException
854 * If either {@code off} or {@code len} is negative, or if
855 * {@code off+len} is greater than {@code b.length}.
856 *
857 * @throws SecurityException
858 * If an attempt is made to add this class to a package that
859 * contains classes that were signed by a different set of
860 * certificates than this class (which is unsigned), or if
861 * {@code name} begins with "{@code java.}".
862 *
863 * @see #loadClass(String, boolean)
864 * @see #resolveClass(Class)
865 * @see java.security.CodeSource
866 * @see java.security.SecureClassLoader
867 *
868 * @since 1.1
869 * @revised 9
870 * @spec JPMS
871 */
872 protected final Class<?> defineClass(String name, byte[] b, int off, int len)
873 throws ClassFormatError
874 {
875 return defineClass(name, b, off, len, null);
876 }
877
878 /* Determine protection domain, and check that:
879 - not define java.* class,
880 - signer of this class matches signers for the rest of the classes in
881 package.
882 */
883 private ProtectionDomain preDefineClass(String name,
884 ProtectionDomain pd)
885 {
886 if (!checkName(name))
887 throw new NoClassDefFoundError("IllegalName: " + name);
888
889 // Note: Checking logic in java.lang.invoke.MemberName.checkForTypeAlias
890 // relies on the fact that spoofing is impossible if a class has a name
891 // of the form "java.*"
892 if ((name != null) && name.startsWith("java.")
893 && this != getBuiltinPlatformClassLoader()) {
894 throw new SecurityException
895 ("Prohibited package name: " +
896 name.substring(0, name.lastIndexOf('.')));
897 }
898 if (pd == null) {
899 pd = defaultDomain;
900 }
901
902 if (name != null) {
903 checkCerts(name, pd.getCodeSource());
904 }
905
906 return pd;
907 }
908
909 private String defineClassSourceLocation(ProtectionDomain pd) {
910 CodeSource cs = pd.getCodeSource();
911 String source = null;
912 if (cs != null && cs.getLocation() != null) {
913 source = cs.getLocation().toString();
914 }
915 return source;
916 }
917
918 private void postDefineClass(Class<?> c, ProtectionDomain pd) {
919 // define a named package, if not present
920 getNamedPackage(c.getPackageName(), c.getModule());
921
922 if (pd.getCodeSource() != null) {
923 Certificate certs[] = pd.getCodeSource().getCertificates();
924 if (certs != null)
925 setSigners(c, certs);
926 }
927 }
928
929 /**
930 * Converts an array of bytes into an instance of class {@code Class},
931 * with a given {@code ProtectionDomain}.
932 *
933 * <p> If the given {@code ProtectionDomain} is {@code null},
934 * then a default protection domain will be assigned to the class as specified
935 * in the documentation for {@link #defineClass(String, byte[], int, int)}.
936 * Before the class can be used it must be resolved.
937 *
938 * <p> The first class defined in a package determines the exact set of
939 * certificates that all subsequent classes defined in that package must
940 * contain. The set of certificates for a class is obtained from the
941 * {@link java.security.CodeSource CodeSource} within the
942 * {@code ProtectionDomain} of the class. Any classes added to that
943 * package must contain the same set of certificates or a
944 * {@code SecurityException} will be thrown. Note that if
945 * {@code name} is {@code null}, this check is not performed.
946 * You should always pass in the <a href="#binary-name">binary name</a> of the
947 * class you are defining as well as the bytes. This ensures that the
948 * class you are defining is indeed the class you think it is.
949 *
950 * <p> If the specified {@code name} begins with "{@code java.}", it can
951 * only be defined by the {@linkplain #getPlatformClassLoader()
952 * platform class loader} or its ancestors; otherwise {@code SecurityException}
953 * will be thrown. If {@code name} is not {@code null}, it must be equal to
954 * the <a href="#binary-name">binary name</a> of the class
955 * specified by the byte array {@code b}, otherwise a {@link
956 * NoClassDefFoundError NoClassDefFoundError} will be thrown.
957 *
958 * <p> This method defines a package in this class loader corresponding to the
959 * package of the {@code Class} (if such a package has not already been defined
960 * in this class loader). The name of the defined package is derived from
961 * the <a href="#binary-name">binary name</a> of the class specified by
962 * the byte array {@code b}.
963 * Other properties of the defined package are as specified by {@link Package}.
964 *
965 * @param name
966 * The expected <a href="#binary-name">binary name</a> of the class, or
967 * {@code null} if not known
968 *
969 * @param b
970 * The bytes that make up the class data. The bytes in positions
971 * {@code off} through {@code off+len-1} should have the format
972 * of a valid class file as defined by
973 * <cite>The Java™ Virtual Machine Specification</cite>.
974 *
975 * @param off
976 * The start offset in {@code b} of the class data
977 *
978 * @param len
979 * The length of the class data
980 *
981 * @param protectionDomain
982 * The {@code ProtectionDomain} of the class
983 *
984 * @return The {@code Class} object created from the data,
985 * and {@code ProtectionDomain}.
986 *
987 * @throws ClassFormatError
988 * If the data did not contain a valid class
989 *
990 * @throws NoClassDefFoundError
991 * If {@code name} is not {@code null} and not equal to the
992 * <a href="#binary-name">binary name</a> of the class specified by {@code b}
993 *
994 * @throws IndexOutOfBoundsException
995 * If either {@code off} or {@code len} is negative, or if
996 * {@code off+len} is greater than {@code b.length}.
997 *
998 * @throws SecurityException
999 * If an attempt is made to add this class to a package that
1000 * contains classes that were signed by a different set of
1001 * certificates than this class, or if {@code name} begins with
1002 * "{@code java.}" and this class loader is not the platform
1003 * class loader or its ancestor.
1004 *
1005 * @revised 9
1006 * @spec JPMS
1007 */
1008 protected final Class<?> defineClass(String name, byte[] b, int off, int len,
1009 ProtectionDomain protectionDomain)
1010 throws ClassFormatError
1011 {
1012 protectionDomain = preDefineClass(name, protectionDomain);
1013 String source = defineClassSourceLocation(protectionDomain);
1014 Class<?> c = defineClass1(this, name, b, off, len, protectionDomain, source);
1015 postDefineClass(c, protectionDomain);
1016 return c;
1017 }
1018
1019 /**
1020 * Converts a {@link java.nio.ByteBuffer ByteBuffer} into an instance
1021 * of class {@code Class}, with the given {@code ProtectionDomain}.
1022 * If the given {@code ProtectionDomain} is {@code null}, then a default
1023 * protection domain will be assigned to the class as
1024 * specified in the documentation for {@link #defineClass(String, byte[],
1025 * int, int)}. Before the class can be used it must be resolved.
1026 *
1027 * <p>The rules about the first class defined in a package determining the
1028 * set of certificates for the package, the restrictions on class names,
1029 * and the defined package of the class
1030 * are identical to those specified in the documentation for {@link
1031 * #defineClass(String, byte[], int, int, ProtectionDomain)}.
1032 *
1033 * <p> An invocation of this method of the form
1034 * <i>cl</i>{@code .defineClass(}<i>name</i>{@code ,}
1035 * <i>bBuffer</i>{@code ,} <i>pd</i>{@code )} yields exactly the same
1036 * result as the statements
1037 *
1038 *<p> <code>
1039 * ...<br>
1040 * byte[] temp = new byte[bBuffer.{@link
1041 * java.nio.ByteBuffer#remaining remaining}()];<br>
1042 * bBuffer.{@link java.nio.ByteBuffer#get(byte[])
1043 * get}(temp);<br>
1044 * return {@link #defineClass(String, byte[], int, int, ProtectionDomain)
1045 * cl.defineClass}(name, temp, 0,
1046 * temp.length, pd);<br>
1047 * </code></p>
1048 *
1049 * @param name
1050 * The expected <a href="#binary-name">binary name</a>. of the class, or
1051 * {@code null} if not known
1052 *
1053 * @param b
1054 * The bytes that make up the class data. The bytes from positions
1055 * {@code b.position()} through {@code b.position() + b.limit() -1
1056 * } should have the format of a valid class file as defined by
1057 * <cite>The Java™ Virtual Machine Specification</cite>.
1058 *
1059 * @param protectionDomain
1060 * The {@code ProtectionDomain} of the class, or {@code null}.
1061 *
1062 * @return The {@code Class} object created from the data,
1063 * and {@code ProtectionDomain}.
1064 *
1065 * @throws ClassFormatError
1066 * If the data did not contain a valid class.
1067 *
1068 * @throws NoClassDefFoundError
1069 * If {@code name} is not {@code null} and not equal to the
1070 * <a href="#binary-name">binary name</a> of the class specified by {@code b}
1071 *
1072 * @throws SecurityException
1073 * If an attempt is made to add this class to a package that
1074 * contains classes that were signed by a different set of
1075 * certificates than this class, or if {@code name} begins with
1076 * "{@code java.}".
1077 *
1078 * @see #defineClass(String, byte[], int, int, ProtectionDomain)
1079 *
1080 * @since 1.5
1081 * @revised 9
1082 * @spec JPMS
1083 */
1084 protected final Class<?> defineClass(String name, java.nio.ByteBuffer b,
1085 ProtectionDomain protectionDomain)
1086 throws ClassFormatError
1087 {
1088 int len = b.remaining();
1089
1090 // Use byte[] if not a direct ByteBuffer:
1091 if (!b.isDirect()) {
1092 if (b.hasArray()) {
1093 return defineClass(name, b.array(),
1094 b.position() + b.arrayOffset(), len,
1095 protectionDomain);
1096 } else {
1097 // no array, or read-only array
1098 byte[] tb = new byte[len];
1099 b.get(tb); // get bytes out of byte buffer.
1100 return defineClass(name, tb, 0, len, protectionDomain);
1101 }
1102 }
1103
1104 protectionDomain = preDefineClass(name, protectionDomain);
1105 String source = defineClassSourceLocation(protectionDomain);
1106 Class<?> c = defineClass2(this, name, b, b.position(), len, protectionDomain, source);
1107 postDefineClass(c, protectionDomain);
1108 return c;
1109 }
1110
1111 static native Class<?> defineClass1(ClassLoader loader, String name, byte[] b, int off, int len,
1112 ProtectionDomain pd, String source);
1113
1114 static native Class<?> defineClass2(ClassLoader loader, String name, java.nio.ByteBuffer b,
1115 int off, int len, ProtectionDomain pd,
1116 String source);
1117
1118 // true if the name is null or has the potential to be a valid binary name
1119 private boolean checkName(String name) {
1120 if ((name == null) || (name.isEmpty()))
1121 return true;
1122 if ((name.indexOf('/') != -1) || (name.charAt(0) == '['))
1123 return false;
1124 return true;
1125 }
1126
1127 private void checkCerts(String name, CodeSource cs) {
1128 int i = name.lastIndexOf('.');
1129 String pname = (i == -1) ? "" : name.substring(0, i);
1130
1131 Certificate[] certs = null;
1132 if (cs != null) {
1133 certs = cs.getCertificates();
1134 }
1135 certs = certs == null ? nocerts : certs;
1136 Certificate[] pcerts = package2certs.putIfAbsent(pname, certs);
1137 if (pcerts != null && !compareCerts(pcerts, certs)) {
1138 throw new SecurityException("class \"" + name
1139 + "\"'s signer information does not match signer information"
1140 + " of other classes in the same package");
1141 }
1142 }
1143
1144 /**
1145 * check to make sure the certs for the new class (certs) are the same as
1146 * the certs for the first class inserted in the package (pcerts)
1147 */
1148 private boolean compareCerts(Certificate[] pcerts, Certificate[] certs) {
1149 // empty array fast-path
1150 if (certs.length == 0)
1151 return pcerts.length == 0;
1152
1153 // the length must be the same at this point
1154 if (certs.length != pcerts.length)
1155 return false;
1156
1157 // go through and make sure all the certs in one array
1158 // are in the other and vice-versa.
1159 boolean match;
1160 for (Certificate cert : certs) {
1161 match = false;
1162 for (Certificate pcert : pcerts) {
1163 if (cert.equals(pcert)) {
1164 match = true;
1165 break;
1166 }
1167 }
1168 if (!match) return false;
1169 }
1170
1171 // now do the same for pcerts
1172 for (Certificate pcert : pcerts) {
1173 match = false;
1174 for (Certificate cert : certs) {
1175 if (pcert.equals(cert)) {
1176 match = true;
1177 break;
1178 }
1179 }
1180 if (!match) return false;
1181 }
1182
1183 return true;
1184 }
1185
1186 /**
1187 * Links the specified class. This (misleadingly named) method may be
1188 * used by a class loader to link a class. If the class {@code c} has
1189 * already been linked, then this method simply returns. Otherwise, the
1190 * class is linked as described in the "Execution" chapter of
1191 * <cite>The Java™ Language Specification</cite>.
1192 *
1193 * @param c
1194 * The class to link
1195 *
1196 * @throws NullPointerException
1197 * If {@code c} is {@code null}.
1198 *
1199 * @see #defineClass(String, byte[], int, int)
1200 */
1201 protected final void resolveClass(Class<?> c) {
1202 if (c == null) {
1203 throw new NullPointerException();
1204 }
1205 }
1206
1207 /**
1208 * Finds a class with the specified <a href="#binary-name">binary name</a>,
1209 * loading it if necessary.
1210 *
1211 * <p> This method loads the class through the system class loader (see
1212 * {@link #getSystemClassLoader()}). The {@code Class} object returned
1213 * might have more than one {@code ClassLoader} associated with it.
1214 * Subclasses of {@code ClassLoader} need not usually invoke this method,
1215 * because most class loaders need to override just {@link
1216 * #findClass(String)}. </p>
1217 *
1218 * @param name
1219 * The <a href="#binary-name">binary name</a> of the class
1220 *
1221 * @return The {@code Class} object for the specified {@code name}
1222 *
1223 * @throws ClassNotFoundException
1224 * If the class could not be found
1225 *
1226 * @see #ClassLoader(ClassLoader)
1227 * @see #getParent()
1228 */
1229 protected final Class<?> findSystemClass(String name)
1230 throws ClassNotFoundException
1231 {
1232 return getSystemClassLoader().loadClass(name);
1233 }
1234
1235 /**
1236 * Returns a class loaded by the bootstrap class loader;
1237 * or return null if not found.
1238 */
1239 Class<?> findBootstrapClassOrNull(String name) {
1240 if (!checkName(name)) return null;
1241
1242 return findBootstrapClass(name);
1243 }
1244
1245 // return null if not found
1246 private native Class<?> findBootstrapClass(String name);
1247
1248 /**
1249 * Returns the class with the given <a href="#binary-name">binary name</a> if this
1250 * loader has been recorded by the Java virtual machine as an initiating
1251 * loader of a class with that <a href="#binary-name">binary name</a>. Otherwise
1252 * {@code null} is returned.
1253 *
1254 * @param name
1255 * The <a href="#binary-name">binary name</a> of the class
1256 *
1257 * @return The {@code Class} object, or {@code null} if the class has
1258 * not been loaded
1259 *
1260 * @since 1.1
1261 */
1262 protected final Class<?> findLoadedClass(String name) {
1263 if (!checkName(name))
1264 return null;
1265 return findLoadedClass0(name);
1266 }
1267
1268 private final native Class<?> findLoadedClass0(String name);
1269
1270 /**
1271 * Sets the signers of a class. This should be invoked after defining a
1272 * class.
1273 *
1274 * @param c
1275 * The {@code Class} object
1276 *
1277 * @param signers
1278 * The signers for the class
1279 *
1280 * @since 1.1
1281 */
1282 protected final void setSigners(Class<?> c, Object[] signers) {
1283 c.setSigners(signers);
1284 }
1285
1286
1287 // -- Resources --
1288
1289 /**
1290 * Returns a URL to a resource in a module defined to this class loader.
1291 * Class loader implementations that support loading from modules
1292 * should override this method.
1293 *
1294 * @apiNote This method is the basis for the {@link
1295 * Class#getResource Class.getResource}, {@link Class#getResourceAsStream
1296 * Class.getResourceAsStream}, and {@link Module#getResourceAsStream
1297 * Module.getResourceAsStream} methods. It is not subject to the rules for
1298 * encapsulation specified by {@code Module.getResourceAsStream}.
1299 *
1300 * @implSpec The default implementation attempts to find the resource by
1301 * invoking {@link #findResource(String)} when the {@code moduleName} is
1302 * {@code null}. It otherwise returns {@code null}.
1303 *
1304 * @param moduleName
1305 * The module name; or {@code null} to find a resource in the
1306 * {@linkplain #getUnnamedModule() unnamed module} for this
1307 * class loader
1308 * @param name
1309 * The resource name
1310 *
1311 * @return A URL to the resource; {@code null} if the resource could not be
1312 * found, a URL could not be constructed to locate the resource,
1313 * access to the resource is denied by the security manager, or
1314 * there isn't a module of the given name defined to the class
1315 * loader.
1316 *
1317 * @throws IOException
1318 * If I/O errors occur
1319 *
1320 * @see java.lang.module.ModuleReader#find(String)
1321 * @since 9
1322 * @spec JPMS
1323 */
1324 protected URL findResource(String moduleName, String name) throws IOException {
1325 if (moduleName == null) {
1326 return findResource(name);
1327 } else {
1328 return null;
1329 }
1330 }
1331
1332 /**
1333 * Finds the resource with the given name. A resource is some data
1334 * (images, audio, text, etc) that can be accessed by class code in a way
1335 * that is independent of the location of the code.
1336 *
1337 * <p> The name of a resource is a '{@code /}'-separated path name that
1338 * identifies the resource. </p>
1339 *
1340 * <p> Resources in named modules are subject to the encapsulation rules
1341 * specified by {@link Module#getResourceAsStream Module.getResourceAsStream}.
1342 * Additionally, and except for the special case where the resource has a
1343 * name ending with "{@code .class}", this method will only find resources in
1344 * packages of named modules when the package is {@link Module#isOpen(String)
1345 * opened} unconditionally (even if the caller of this method is in the
1346 * same module as the resource). </p>
1347 *
1348 * @implSpec The default implementation will first search the parent class
1349 * loader for the resource; if the parent is {@code null} the path of the
1350 * class loader built into the virtual machine is searched. If not found,
1351 * this method will invoke {@link #findResource(String)} to find the resource.
1352 *
1353 * @apiNote Where several modules are defined to the same class loader,
1354 * and where more than one module contains a resource with the given name,
1355 * then the ordering that modules are searched is not specified and may be
1356 * very unpredictable.
1357 * When overriding this method it is recommended that an implementation
1358 * ensures that any delegation is consistent with the {@link
1359 * #getResources(java.lang.String) getResources(String)} method.
1360 *
1361 * @param name
1362 * The resource name
1363 *
1364 * @return {@code URL} object for reading the resource; {@code null} if
1365 * the resource could not be found, a {@code URL} could not be
1366 * constructed to locate the resource, the resource is in a package
1367 * that is not opened unconditionally, or access to the resource is
1368 * denied by the security manager.
1369 *
1370 * @throws NullPointerException If {@code name} is {@code null}
1371 *
1372 * @since 1.1
1373 * @revised 9
1374 * @spec JPMS
1375 */
1376 public URL getResource(String name) {
1377 Objects.requireNonNull(name);
1378 URL url;
1379 if (parent != null) {
1380 url = parent.getResource(name);
1381 } else {
1382 url = BootLoader.findResource(name);
1383 }
1384 if (url == null) {
1385 url = findResource(name);
1386 }
1387 return url;
1388 }
1389
1390 /**
1391 * Finds all the resources with the given name. A resource is some data
1392 * (images, audio, text, etc) that can be accessed by class code in a way
1393 * that is independent of the location of the code.
1394 *
1395 * <p> The name of a resource is a {@code /}-separated path name that
1396 * identifies the resource. </p>
1397 *
1398 * <p> Resources in named modules are subject to the encapsulation rules
1399 * specified by {@link Module#getResourceAsStream Module.getResourceAsStream}.
1400 * Additionally, and except for the special case where the resource has a
1401 * name ending with "{@code .class}", this method will only find resources in
1402 * packages of named modules when the package is {@link Module#isOpen(String)
1403 * opened} unconditionally (even if the caller of this method is in the
1404 * same module as the resource). </p>
1405 *
1406 * @implSpec The default implementation will first search the parent class
1407 * loader for the resource; if the parent is {@code null} the path of the
1408 * class loader built into the virtual machine is searched. It then
1409 * invokes {@link #findResources(String)} to find the resources with the
1410 * name in this class loader. It returns an enumeration whose elements
1411 * are the URLs found by searching the parent class loader followed by
1412 * the elements found with {@code findResources}.
1413 *
1414 * @apiNote Where several modules are defined to the same class loader,
1415 * and where more than one module contains a resource with the given name,
1416 * then the ordering is not specified and may be very unpredictable.
1417 * When overriding this method it is recommended that an
1418 * implementation ensures that any delegation is consistent with the {@link
1419 * #getResource(java.lang.String) getResource(String)} method. This should
1420 * ensure that the first element returned by the Enumeration's
1421 * {@code nextElement} method is the same resource that the
1422 * {@code getResource(String)} method would return.
1423 *
1424 * @param name
1425 * The resource name
1426 *
1427 * @return An enumeration of {@link java.net.URL URL} objects for the
1428 * resource. If no resources could be found, the enumeration will
1429 * be empty. Resources for which a {@code URL} cannot be
1430 * constructed, are in a package that is not opened
1431 * unconditionally, or access to the resource is denied by the
1432 * security manager, are not returned in the enumeration.
1433 *
1434 * @throws IOException
1435 * If I/O errors occur
1436 * @throws NullPointerException If {@code name} is {@code null}
1437 *
1438 * @since 1.2
1439 * @revised 9
1440 * @spec JPMS
1441 */
1442 public Enumeration<URL> getResources(String name) throws IOException {
1443 Objects.requireNonNull(name);
1444 @SuppressWarnings("unchecked")
1445 Enumeration<URL>[] tmp = (Enumeration<URL>[]) new Enumeration<?>[2];
1446 if (parent != null) {
1447 tmp[0] = parent.getResources(name);
1448 } else {
1449 tmp[0] = BootLoader.findResources(name);
1450 }
1451 tmp[1] = findResources(name);
1452
1453 return new CompoundEnumeration<>(tmp);
1454 }
1455
1456 /**
1457 * Returns a stream whose elements are the URLs of all the resources with
1458 * the given name. A resource is some data (images, audio, text, etc) that
1459 * can be accessed by class code in a way that is independent of the
1460 * location of the code.
1461 *
1462 * <p> The name of a resource is a {@code /}-separated path name that
1463 * identifies the resource.
1464 *
1465 * <p> The resources will be located when the returned stream is evaluated.
1466 * If the evaluation results in an {@code IOException} then the I/O
1467 * exception is wrapped in an {@link UncheckedIOException} that is then
1468 * thrown.
1469 *
1470 * <p> Resources in named modules are subject to the encapsulation rules
1471 * specified by {@link Module#getResourceAsStream Module.getResourceAsStream}.
1472 * Additionally, and except for the special case where the resource has a
1473 * name ending with "{@code .class}", this method will only find resources in
1474 * packages of named modules when the package is {@link Module#isOpen(String)
1475 * opened} unconditionally (even if the caller of this method is in the
1476 * same module as the resource). </p>
1477 *
1478 * @implSpec The default implementation invokes {@link #getResources(String)
1479 * getResources} to find all the resources with the given name and returns
1480 * a stream with the elements in the enumeration as the source.
1481 *
1482 * @apiNote When overriding this method it is recommended that an
1483 * implementation ensures that any delegation is consistent with the {@link
1484 * #getResource(java.lang.String) getResource(String)} method. This should
1485 * ensure that the first element returned by the stream is the same
1486 * resource that the {@code getResource(String)} method would return.
1487 *
1488 * @param name
1489 * The resource name
1490 *
1491 * @return A stream of resource {@link java.net.URL URL} objects. If no
1492 * resources could be found, the stream will be empty. Resources
1493 * for which a {@code URL} cannot be constructed, are in a package
1494 * that is not opened unconditionally, or access to the resource
1495 * is denied by the security manager, will not be in the stream.
1496 *
1497 * @throws NullPointerException If {@code name} is {@code null}
1498 *
1499 * @since 9
1500 */
1501 public Stream<URL> resources(String name) {
1502 Objects.requireNonNull(name);
1503 int characteristics = Spliterator.NONNULL | Spliterator.IMMUTABLE;
1504 Supplier<Spliterator<URL>> si = () -> {
1505 try {
1506 return Spliterators.spliteratorUnknownSize(
1507 getResources(name).asIterator(), characteristics);
1508 } catch (IOException e) {
1509 throw new UncheckedIOException(e);
1510 }
1511 };
1512 return StreamSupport.stream(si, characteristics, false);
1513 }
1514
1515 /**
1516 * Finds the resource with the given name. Class loader implementations
1517 * should override this method.
1518 *
1519 * <p> For resources in named modules then the method must implement the
1520 * rules for encapsulation specified in the {@code Module} {@link
1521 * Module#getResourceAsStream getResourceAsStream} method. Additionally,
1522 * it must not find non-"{@code .class}" resources in packages of named
1523 * modules unless the package is {@link Module#isOpen(String) opened}
1524 * unconditionally. </p>
1525 *
1526 * @implSpec The default implementation returns {@code null}.
1527 *
1528 * @param name
1529 * The resource name
1530 *
1531 * @return {@code URL} object for reading the resource; {@code null} if
1532 * the resource could not be found, a {@code URL} could not be
1533 * constructed to locate the resource, the resource is in a package
1534 * that is not opened unconditionally, or access to the resource is
1535 * denied by the security manager.
1536 *
1537 * @since 1.2
1538 * @revised 9
1539 * @spec JPMS
1540 */
1541 protected URL findResource(String name) {
1542 return null;
1543 }
1544
1545 /**
1546 * Returns an enumeration of {@link java.net.URL URL} objects
1547 * representing all the resources with the given name. Class loader
1548 * implementations should override this method.
1549 *
1550 * <p> For resources in named modules then the method must implement the
1551 * rules for encapsulation specified in the {@code Module} {@link
1552 * Module#getResourceAsStream getResourceAsStream} method. Additionally,
1553 * it must not find non-"{@code .class}" resources in packages of named
1554 * modules unless the package is {@link Module#isOpen(String) opened}
1555 * unconditionally. </p>
1556 *
1557 * @implSpec The default implementation returns an enumeration that
1558 * contains no elements.
1559 *
1560 * @param name
1561 * The resource name
1562 *
1563 * @return An enumeration of {@link java.net.URL URL} objects for
1564 * the resource. If no resources could be found, the enumeration
1565 * will be empty. Resources for which a {@code URL} cannot be
1566 * constructed, are in a package that is not opened unconditionally,
1567 * or access to the resource is denied by the security manager,
1568 * are not returned in the enumeration.
1569 *
1570 * @throws IOException
1571 * If I/O errors occur
1572 *
1573 * @since 1.2
1574 * @revised 9
1575 * @spec JPMS
1576 */
1577 protected Enumeration<URL> findResources(String name) throws IOException {
1578 return Collections.emptyEnumeration();
1579 }
1580
1581 /**
1582 * Registers the caller as
1583 * {@linkplain #isRegisteredAsParallelCapable() parallel capable}.
1584 * The registration succeeds if and only if all of the following
1585 * conditions are met:
1586 * <ol>
1587 * <li> no instance of the caller has been created</li>
1588 * <li> all of the super classes (except class Object) of the caller are
1589 * registered as parallel capable</li>
1590 * </ol>
1591 * <p>Note that once a class loader is registered as parallel capable, there
1592 * is no way to change it back.</p>
1593 *
1594 * @return {@code true} if the caller is successfully registered as
1595 * parallel capable and {@code false} if otherwise.
1596 *
1597 * @see #isRegisteredAsParallelCapable()
1598 *
1599 * @since 1.7
1600 */
1601 @CallerSensitive
1602 protected static boolean registerAsParallelCapable() {
1603 Class<? extends ClassLoader> callerClass =
1604 Reflection.getCallerClass().asSubclass(ClassLoader.class);
1605 return ParallelLoaders.register(callerClass);
1606 }
1607
1608 /**
1609 * Returns {@code true} if this class loader is registered as
1610 * {@linkplain #registerAsParallelCapable parallel capable}, otherwise
1611 * {@code false}.
1612 *
1613 * @return {@code true} if this class loader is parallel capable,
1614 * otherwise {@code false}.
1615 *
1616 * @see #registerAsParallelCapable()
1617 *
1618 * @since 9
1619 */
1620 public final boolean isRegisteredAsParallelCapable() {
1621 return ParallelLoaders.isRegistered(this.getClass());
1622 }
1623
1624 /**
1625 * Find a resource of the specified name from the search path used to load
1626 * classes. This method locates the resource through the system class
1627 * loader (see {@link #getSystemClassLoader()}).
1628 *
1629 * <p> Resources in named modules are subject to the encapsulation rules
1630 * specified by {@link Module#getResourceAsStream Module.getResourceAsStream}.
1631 * Additionally, and except for the special case where the resource has a
1632 * name ending with "{@code .class}", this method will only find resources in
1633 * packages of named modules when the package is {@link Module#isOpen(String)
1634 * opened} unconditionally. </p>
1635 *
1636 * @param name
1637 * The resource name
1638 *
1639 * @return A {@link java.net.URL URL} to the resource; {@code
1640 * null} if the resource could not be found, a URL could not be
1641 * constructed to locate the resource, the resource is in a package
1642 * that is not opened unconditionally or access to the resource is
1643 * denied by the security manager.
1644 *
1645 * @since 1.1
1646 * @revised 9
1647 * @spec JPMS
1648 */
1649 public static URL getSystemResource(String name) {
1650 return getSystemClassLoader().getResource(name);
1651 }
1652
1653 /**
1654 * Finds all resources of the specified name from the search path used to
1655 * load classes. The resources thus found are returned as an
1656 * {@link java.util.Enumeration Enumeration} of {@link
1657 * java.net.URL URL} objects.
1658 *
1659 * <p> The search order is described in the documentation for {@link
1660 * #getSystemResource(String)}. </p>
1661 *
1662 * <p> Resources in named modules are subject to the encapsulation rules
1663 * specified by {@link Module#getResourceAsStream Module.getResourceAsStream}.
1664 * Additionally, and except for the special case where the resource has a
1665 * name ending with "{@code .class}", this method will only find resources in
1666 * packages of named modules when the package is {@link Module#isOpen(String)
1667 * opened} unconditionally. </p>
1668 *
1669 * @param name
1670 * The resource name
1671 *
1672 * @return An enumeration of {@link java.net.URL URL} objects for
1673 * the resource. If no resources could be found, the enumeration
1674 * will be empty. Resources for which a {@code URL} cannot be
1675 * constructed, are in a package that is not opened unconditionally,
1676 * or access to the resource is denied by the security manager,
1677 * are not returned in the enumeration.
1678 *
1679 * @throws IOException
1680 * If I/O errors occur
1681 *
1682 * @since 1.2
1683 * @revised 9
1684 * @spec JPMS
1685 */
1686 public static Enumeration<URL> getSystemResources(String name)
1687 throws IOException
1688 {
1689 return getSystemClassLoader().getResources(name);
1690 }
1691
1692 /**
1693 * Returns an input stream for reading the specified resource.
1694 *
1695 * <p> The search order is described in the documentation for {@link
1696 * #getResource(String)}. </p>
1697 *
1698 * <p> Resources in named modules are subject to the encapsulation rules
1699 * specified by {@link Module#getResourceAsStream Module.getResourceAsStream}.
1700 * Additionally, and except for the special case where the resource has a
1701 * name ending with "{@code .class}", this method will only find resources in
1702 * packages of named modules when the package is {@link Module#isOpen(String)
1703 * opened} unconditionally. </p>
1704 *
1705 * @param name
1706 * The resource name
1707 *
1708 * @return An input stream for reading the resource; {@code null} if the
1709 * resource could not be found, the resource is in a package that
1710 * is not opened unconditionally, or access to the resource is
1711 * denied by the security manager.
1712 *
1713 * @throws NullPointerException If {@code name} is {@code null}
1714 *
1715 * @since 1.1
1716 * @revised 9
1717 * @spec JPMS
1718 */
1719 public InputStream getResourceAsStream(String name) {
1720 Objects.requireNonNull(name);
1721 URL url = getResource(name);
1722 try {
1723 return url != null ? url.openStream() : null;
1724 } catch (IOException e) {
1725 return null;
1726 }
1727 }
1728
1729 /**
1730 * Open for reading, a resource of the specified name from the search path
1731 * used to load classes. This method locates the resource through the
1732 * system class loader (see {@link #getSystemClassLoader()}).
1733 *
1734 * <p> Resources in named modules are subject to the encapsulation rules
1735 * specified by {@link Module#getResourceAsStream Module.getResourceAsStream}.
1736 * Additionally, and except for the special case where the resource has a
1737 * name ending with "{@code .class}", this method will only find resources in
1738 * packages of named modules when the package is {@link Module#isOpen(String)
1739 * opened} unconditionally. </p>
1740 *
1741 * @param name
1742 * The resource name
1743 *
1744 * @return An input stream for reading the resource; {@code null} if the
1745 * resource could not be found, the resource is in a package that
1746 * is not opened unconditionally, or access to the resource is
1747 * denied by the security manager.
1748 *
1749 * @since 1.1
1750 * @revised 9
1751 * @spec JPMS
1752 */
1753 public static InputStream getSystemResourceAsStream(String name) {
1754 URL url = getSystemResource(name);
1755 try {
1756 return url != null ? url.openStream() : null;
1757 } catch (IOException e) {
1758 return null;
1759 }
1760 }
1761
1762
1763 // -- Hierarchy --
1764
1765 /**
1766 * Returns the parent class loader for delegation. Some implementations may
1767 * use {@code null} to represent the bootstrap class loader. This method
1768 * will return {@code null} in such implementations if this class loader's
1769 * parent is the bootstrap class loader.
1770 *
1771 * @return The parent {@code ClassLoader}
1772 *
1773 * @throws SecurityException
1774 * If a security manager is present, and the caller's class loader
1775 * is not {@code null} and is not an ancestor of this class loader,
1776 * and the caller does not have the
1777 * {@link RuntimePermission}{@code ("getClassLoader")}
1778 *
1779 * @since 1.2
1780 */
1781 @CallerSensitive
1782 public final ClassLoader getParent() {
1783 if (parent == null)
1784 return null;
1785 SecurityManager sm = System.getSecurityManager();
1786 if (sm != null) {
1787 // Check access to the parent class loader
1788 // If the caller's class loader is same as this class loader,
1789 // permission check is performed.
1790 checkClassLoaderPermission(parent, Reflection.getCallerClass());
1791 }
1792 return parent;
1793 }
1794
1795 /**
1796 * Returns the unnamed {@code Module} for this class loader.
1797 *
1798 * @return The unnamed Module for this class loader
1799 *
1800 * @see Module#isNamed()
1801 * @since 9
1802 * @spec JPMS
1803 */
1804 public final Module getUnnamedModule() {
1805 return unnamedModule;
1806 }
1807
1808 /**
1809 * Returns the platform class loader. All
1810 * <a href="#builtinLoaders">platform classes</a> are visible to
1811 * the platform class loader.
1812 *
1813 * @implNote The name of the builtin platform class loader is
1814 * {@code "platform"}.
1815 *
1816 * @return The platform {@code ClassLoader}.
1817 *
1818 * @throws SecurityException
1819 * If a security manager is present, and the caller's class loader is
1820 * not {@code null}, and the caller's class loader is not the same
1821 * as or an ancestor of the platform class loader,
1822 * and the caller does not have the
1823 * {@link RuntimePermission}{@code ("getClassLoader")}
1824 *
1825 * @since 9
1826 * @spec JPMS
1827 */
1828 @CallerSensitive
1829 public static ClassLoader getPlatformClassLoader() {
1830 SecurityManager sm = System.getSecurityManager();
1831 ClassLoader loader = getBuiltinPlatformClassLoader();
1832 if (sm != null) {
1833 checkClassLoaderPermission(loader, Reflection.getCallerClass());
1834 }
1835 return loader;
1836 }
1837
1838 /**
1839 * Returns the system class loader. This is the default
1840 * delegation parent for new {@code ClassLoader} instances, and is
1841 * typically the class loader used to start the application.
1842 *
1843 * <p> This method is first invoked early in the runtime's startup
1844 * sequence, at which point it creates the system class loader. This
1845 * class loader will be the context class loader for the main application
1846 * thread (for example, the thread that invokes the {@code main} method of
1847 * the main class).
1848 *
1849 * <p> The default system class loader is an implementation-dependent
1850 * instance of this class.
1851 *
1852 * <p> If the system property "{@systemProperty java.system.class.loader}"
1853 * is defined when this method is first invoked then the value of that
1854 * property is taken to be the name of a class that will be returned as the
1855 * system class loader. The class is loaded using the default system class
1856 * loader and must define a public constructor that takes a single parameter
1857 * of type {@code ClassLoader} which is used as the delegation parent. An
1858 * instance is then created using this constructor with the default system
1859 * class loader as the parameter. The resulting class loader is defined
1860 * to be the system class loader. During construction, the class loader
1861 * should take great care to avoid calling {@code getSystemClassLoader()}.
1862 * If circular initialization of the system class loader is detected then
1863 * an {@code IllegalStateException} is thrown.
1864 *
1865 * @implNote The system property to override the system class loader is not
1866 * examined until the VM is almost fully initialized. Code that executes
1867 * this method during startup should take care not to cache the return
1868 * value until the system is fully initialized.
1869 *
1870 * <p> The name of the built-in system class loader is {@code "app"}.
1871 * The system property "{@code java.class.path}" is read during early
1872 * initialization of the VM to determine the class path.
1873 * An empty value of "{@code java.class.path}" property is interpreted
1874 * differently depending on whether the initial module (the module
1875 * containing the main class) is named or unnamed:
1876 * If named, the built-in system class loader will have no class path and
1877 * will search for classes and resources using the application module path;
1878 * otherwise, if unnamed, it will set the class path to the current
1879 * working directory.
1880 *
1881 * <p> JAR files on the class path may contain a {@code Class-Path} manifest
1882 * attribute to specify dependent JAR files to be included in the class path.
1883 * {@code Class-Path} entries must meet certain conditions for validity (see
1884 * the <a href="{@docRoot}/../specs/jar/jar.html#class-path-attribute">
1885 * JAR File Specification</a> for details). Invalid {@code Class-Path}
1886 * entries are ignored. For debugging purposes, ignored entries can be
1887 * printed to the console if the
1888 * {@systemProperty jdk.net.URLClassPath.showIgnoredClassPathEntries} system
1889 * property is set to {@code true}.
1890 *
1891 * @return The system {@code ClassLoader}
1892 *
1893 * @throws SecurityException
1894 * If a security manager is present, and the caller's class loader
1895 * is not {@code null} and is not the same as or an ancestor of the
1896 * system class loader, and the caller does not have the
1897 * {@link RuntimePermission}{@code ("getClassLoader")}
1898 *
1899 * @throws IllegalStateException
1900 * If invoked recursively during the construction of the class
1901 * loader specified by the "{@code java.system.class.loader}"
1902 * property.
1903 *
1904 * @throws Error
1905 * If the system property "{@code java.system.class.loader}"
1906 * is defined but the named class could not be loaded, the
1907 * provider class does not define the required constructor, or an
1908 * exception is thrown by that constructor when it is invoked. The
1909 * underlying cause of the error can be retrieved via the
1910 * {@link Throwable#getCause()} method.
1911 *
1912 * @revised 1.4
1913 * @revised 9
1914 * @spec JPMS
1915 */
1916 @CallerSensitive
1917 public static ClassLoader getSystemClassLoader() {
1918 switch (VM.initLevel()) {
1919 case 0:
1920 case 1:
1921 case 2:
1922 // the system class loader is the built-in app class loader during startup
1923 return getBuiltinAppClassLoader();
1924 case 3:
1925 String msg = "getSystemClassLoader cannot be called during the system class loader instantiation";
1926 throw new IllegalStateException(msg);
1927 default:
1928 // system fully initialized
1929 assert VM.isBooted() && scl != null;
1930 SecurityManager sm = System.getSecurityManager();
1931 if (sm != null) {
1932 checkClassLoaderPermission(scl, Reflection.getCallerClass());
1933 }
1934 return scl;
1935 }
1936 }
1937
1938 static ClassLoader getBuiltinPlatformClassLoader() {
1939 return ClassLoaders.platformClassLoader();
1940 }
1941
1942 static ClassLoader getBuiltinAppClassLoader() {
1943 return ClassLoaders.appClassLoader();
1944 }
1945
1946 /*
1947 * Initialize the system class loader that may be a custom class on the
1948 * application class path or application module path.
1949 *
1950 * @see java.lang.System#initPhase3
1951 */
1952 static synchronized ClassLoader initSystemClassLoader() {
1953 if (VM.initLevel() != 3) {
1954 throw new InternalError("system class loader cannot be set at initLevel " +
1955 VM.initLevel());
1956 }
1957
1958 // detect recursive initialization
1959 if (scl != null) {
1960 throw new IllegalStateException("recursive invocation");
1961 }
1962
1963 ClassLoader builtinLoader = getBuiltinAppClassLoader();
1964
1965 // All are privileged frames. No need to call doPrivileged.
1966 String cn = System.getProperty("java.system.class.loader");
1967 if (cn != null) {
1968 try {
1969 // custom class loader is only supported to be loaded from unnamed module
1970 Constructor<?> ctor = Class.forName(cn, false, builtinLoader)
1971 .getDeclaredConstructor(ClassLoader.class);
1972 scl = (ClassLoader) ctor.newInstance(builtinLoader);
1973 } catch (Exception e) {
1974 Throwable cause = e;
1975 if (e instanceof InvocationTargetException) {
1976 cause = e.getCause();
1977 if (cause instanceof Error) {
1978 throw (Error) cause;
1979 }
1980 }
1981 if (cause instanceof RuntimeException) {
1982 throw (RuntimeException) cause;
1983 }
1984 throw new Error(cause.getMessage(), cause);
1985 }
1986 } else {
1987 scl = builtinLoader;
1988 }
1989 return scl;
1990 }
1991
1992 // Returns true if the specified class loader can be found in this class
1993 // loader's delegation chain.
1994 boolean isAncestor(ClassLoader cl) {
1995 ClassLoader acl = this;
1996 do {
1997 acl = acl.parent;
1998 if (cl == acl) {
1999 return true;
2000 }
2001 } while (acl != null);
2002 return false;
2003 }
2004
2005 // Tests if class loader access requires "getClassLoader" permission
2006 // check. A class loader 'from' can access class loader 'to' if
2007 // class loader 'from' is same as class loader 'to' or an ancestor
2008 // of 'to'. The class loader in a system domain can access
2009 // any class loader.
2010 private static boolean needsClassLoaderPermissionCheck(ClassLoader from,
2011 ClassLoader to)
2012 {
2013 if (from == to)
2014 return false;
2015
2016 if (from == null)
2017 return false;
2018
2019 return !to.isAncestor(from);
2020 }
2021
2022 // Returns the class's class loader, or null if none.
2023 static ClassLoader getClassLoader(Class<?> caller) {
2024 // This can be null if the VM is requesting it
2025 if (caller == null) {
2026 return null;
2027 }
2028 // Circumvent security check since this is package-private
2029 return caller.getClassLoader0();
2030 }
2031
2032 /*
2033 * Checks RuntimePermission("getClassLoader") permission
2034 * if caller's class loader is not null and caller's class loader
2035 * is not the same as or an ancestor of the given cl argument.
2036 */
2037 static void checkClassLoaderPermission(ClassLoader cl, Class<?> caller) {
2038 SecurityManager sm = System.getSecurityManager();
2039 if (sm != null) {
2040 // caller can be null if the VM is requesting it
2041 ClassLoader ccl = getClassLoader(caller);
2042 if (needsClassLoaderPermissionCheck(ccl, cl)) {
2043 sm.checkPermission(SecurityConstants.GET_CLASSLOADER_PERMISSION);
2044 }
2045 }
2046 }
2047
2048 // The system class loader
2049 // @GuardedBy("ClassLoader.class")
2050 private static volatile ClassLoader scl;
2051
2052 // -- Package --
2053
2054 /**
2055 * Define a Package of the given Class object.
2056 *
2057 * If the given class represents an array type, a primitive type or void,
2058 * this method returns {@code null}.
2059 *
2060 * This method does not throw IllegalArgumentException.
2061 */
2062 Package definePackage(Class<?> c) {
2063 if (c.isPrimitive() || c.isArray()) {
2064 return null;
2065 }
2066
2067 return definePackage(c.getPackageName(), c.getModule());
2068 }
2069
2070 /**
2071 * Defines a Package of the given name and module
2072 *
2073 * This method does not throw IllegalArgumentException.
2074 *
2075 * @param name package name
2076 * @param m module
2077 */
2078 Package definePackage(String name, Module m) {
2079 if (name.isEmpty() && m.isNamed()) {
2080 throw new InternalError("unnamed package in " + m);
2081 }
2082
2083 // check if Package object is already defined
2084 NamedPackage pkg = packages.get(name);
2085 if (pkg instanceof Package)
2086 return (Package)pkg;
2087
2088 return (Package)packages.compute(name, (n, p) -> toPackage(n, p, m));
2089 }
2090
2091 /*
2092 * Returns a Package object for the named package
2093 */
2094 private Package toPackage(String name, NamedPackage p, Module m) {
2095 // define Package object if the named package is not yet defined
2096 if (p == null)
2097 return NamedPackage.toPackage(name, m);
2098
2099 // otherwise, replace the NamedPackage object with Package object
2100 if (p instanceof Package)
2101 return (Package)p;
2102
2103 return NamedPackage.toPackage(p.packageName(), p.module());
2104 }
2105
2106 /**
2107 * Defines a package by <a href="#binary-name">name</a> in this {@code ClassLoader}.
2108 * <p>
2109 * <a href="#binary-name">Package names</a> must be unique within a class loader and
2110 * cannot be redefined or changed once created.
2111 * <p>
2112 * If a class loader wishes to define a package with specific properties,
2113 * such as version information, then the class loader should call this
2114 * {@code definePackage} method before calling {@code defineClass}.
2115 * Otherwise, the
2116 * {@link #defineClass(String, byte[], int, int, ProtectionDomain) defineClass}
2117 * method will define a package in this class loader corresponding to the package
2118 * of the newly defined class; the properties of this defined package are
2119 * specified by {@link Package}.
2120 *
2121 * @apiNote
2122 * A class loader that wishes to define a package for classes in a JAR
2123 * typically uses the specification and implementation titles, versions, and
2124 * vendors from the JAR's manifest. If the package is specified as
2125 * {@linkplain java.util.jar.Attributes.Name#SEALED sealed} in the JAR's manifest,
2126 * the {@code URL} of the JAR file is typically used as the {@code sealBase}.
2127 * If classes of package {@code 'p'} defined by this class loader
2128 * are loaded from multiple JARs, the {@code Package} object may contain
2129 * different information depending on the first class of package {@code 'p'}
2130 * defined and which JAR's manifest is read first to explicitly define
2131 * package {@code 'p'}.
2132 *
2133 * <p> It is strongly recommended that a class loader does not call this
2134 * method to explicitly define packages in <em>named modules</em>; instead,
2135 * the package will be automatically defined when a class is {@linkplain
2136 * #defineClass(String, byte[], int, int, ProtectionDomain) being defined}.
2137 * If it is desirable to define {@code Package} explicitly, it should ensure
2138 * that all packages in a named module are defined with the properties
2139 * specified by {@link Package}. Otherwise, some {@code Package} objects
2140 * in a named module may be for example sealed with different seal base.
2141 *
2142 * @param name
2143 * The <a href="#binary-name">package name</a>
2144 *
2145 * @param specTitle
2146 * The specification title
2147 *
2148 * @param specVersion
2149 * The specification version
2150 *
2151 * @param specVendor
2152 * The specification vendor
2153 *
2154 * @param implTitle
2155 * The implementation title
2156 *
2157 * @param implVersion
2158 * The implementation version
2159 *
2160 * @param implVendor
2161 * The implementation vendor
2162 *
2163 * @param sealBase
2164 * If not {@code null}, then this package is sealed with
2165 * respect to the given code source {@link java.net.URL URL}
2166 * object. Otherwise, the package is not sealed.
2167 *
2168 * @return The newly defined {@code Package} object
2169 *
2170 * @throws NullPointerException
2171 * if {@code name} is {@code null}.
2172 *
2173 * @throws IllegalArgumentException
2174 * if a package of the given {@code name} is already
2175 * defined by this class loader
2176 *
2177 *
2178 * @since 1.2
2179 * @revised 9
2180 * @spec JPMS
2181 *
2182 * @jvms 5.3 Creation and Loading
2183 * @see <a href="{@docRoot}/../specs/jar/jar.html#package-sealing">
2184 * The JAR File Specification: Package Sealing</a>
2185 */
2186 protected Package definePackage(String name, String specTitle,
2187 String specVersion, String specVendor,
2188 String implTitle, String implVersion,
2189 String implVendor, URL sealBase)
2190 {
2191 Objects.requireNonNull(name);
2192
2193 // definePackage is not final and may be overridden by custom class loader
2194 Package p = new Package(name, specTitle, specVersion, specVendor,
2195 implTitle, implVersion, implVendor,
2196 sealBase, this);
2197
2198 if (packages.putIfAbsent(name, p) != null)
2199 throw new IllegalArgumentException(name);
2200
2201 return p;
2202 }
2203
2204 /**
2205 * Returns a {@code Package} of the given <a href="#binary-name">name</a> that
2206 * has been defined by this class loader.
2207 *
2208 * @param name The <a href="#binary-name">package name</a>
2209 *
2210 * @return The {@code Package} of the given name that has been defined
2211 * by this class loader, or {@code null} if not found
2212 *
2213 * @throws NullPointerException
2214 * if {@code name} is {@code null}.
2215 *
2216 * @jvms 5.3 Creation and Loading
2217 *
2218 * @since 9
2219 * @spec JPMS
2220 */
2221 public final Package getDefinedPackage(String name) {
2222 Objects.requireNonNull(name, "name cannot be null");
2223
2224 NamedPackage p = packages.get(name);
2225 if (p == null)
2226 return null;
2227
2228 return definePackage(name, p.module());
2229 }
2230
2231 /**
2232 * Returns all of the {@code Package}s that have been defined by
2233 * this class loader. The returned array has no duplicated {@code Package}s
2234 * of the same name.
2235 *
2236 * @apiNote This method returns an array rather than a {@code Set} or {@code Stream}
2237 * for consistency with the existing {@link #getPackages} method.
2238 *
2239 * @return The array of {@code Package} objects that have been defined by
2240 * this class loader; or an zero length array if no package has been
2241 * defined by this class loader.
2242 *
2243 * @jvms 5.3 Creation and Loading
2244 *
2245 * @since 9
2246 * @spec JPMS
2247 */
2248 public final Package[] getDefinedPackages() {
2249 return packages().toArray(Package[]::new);
2250 }
2251
2252 /**
2253 * Finds a package by <a href="#binary-name">name</a> in this class loader and its ancestors.
2254 * <p>
2255 * If this class loader defines a {@code Package} of the given name,
2256 * the {@code Package} is returned. Otherwise, the ancestors of
2257 * this class loader are searched recursively (parent by parent)
2258 * for a {@code Package} of the given name.
2259 *
2260 * @apiNote The {@link #getPlatformClassLoader() platform class loader}
2261 * may delegate to the application class loader but the application class
2262 * loader is not its ancestor. When invoked on the platform class loader,
2263 * this method will not find packages defined to the application
2264 * class loader.
2265 *
2266 * @param name
2267 * The <a href="#binary-name">package name</a>
2268 *
2269 * @return The {@code Package} of the given name that has been defined by
2270 * this class loader or its ancestors, or {@code null} if not found.
2271 *
2272 * @throws NullPointerException
2273 * if {@code name} is {@code null}.
2274 *
2275 * @deprecated
2276 * If multiple class loaders delegate to each other and define classes
2277 * with the same package name, and one such loader relies on the lookup
2278 * behavior of {@code getPackage} to return a {@code Package} from
2279 * a parent loader, then the properties exposed by the {@code Package}
2280 * may not be as expected in the rest of the program.
2281 * For example, the {@code Package} will only expose annotations from the
2282 * {@code package-info.class} file defined by the parent loader, even if
2283 * annotations exist in a {@code package-info.class} file defined by
2284 * a child loader. A more robust approach is to use the
2285 * {@link ClassLoader#getDefinedPackage} method which returns
2286 * a {@code Package} for the specified class loader.
2287 *
2288 * @see ClassLoader#getDefinedPackage(String)
2289 *
2290 * @since 1.2
2291 * @revised 9
2292 * @spec JPMS
2293 */
2294 @Deprecated(since="9")
2295 protected Package getPackage(String name) {
2296 Package pkg = getDefinedPackage(name);
2297 if (pkg == null) {
2298 if (parent != null) {
2299 pkg = parent.getPackage(name);
2300 } else {
2301 pkg = BootLoader.getDefinedPackage(name);
2302 }
2303 }
2304 return pkg;
2305 }
2306
2307 /**
2308 * Returns all of the {@code Package}s that have been defined by
2309 * this class loader and its ancestors. The returned array may contain
2310 * more than one {@code Package} object of the same package name, each
2311 * defined by a different class loader in the class loader hierarchy.
2312 *
2313 * @apiNote The {@link #getPlatformClassLoader() platform class loader}
2314 * may delegate to the application class loader. In other words,
2315 * packages in modules defined to the application class loader may be
2316 * visible to the platform class loader. On the other hand,
2317 * the application class loader is not its ancestor and hence
2318 * when invoked on the platform class loader, this method will not
2319 * return any packages defined to the application class loader.
2320 *
2321 * @return The array of {@code Package} objects that have been defined by
2322 * this class loader and its ancestors
2323 *
2324 * @see ClassLoader#getDefinedPackages()
2325 *
2326 * @since 1.2
2327 * @revised 9
2328 * @spec JPMS
2329 */
2330 protected Package[] getPackages() {
2331 Stream<Package> pkgs = packages();
2332 ClassLoader ld = parent;
2333 while (ld != null) {
2334 pkgs = Stream.concat(ld.packages(), pkgs);
2335 ld = ld.parent;
2336 }
2337 return Stream.concat(BootLoader.packages(), pkgs)
2338 .toArray(Package[]::new);
2339 }
2340
2341
2342
2343 // package-private
2344
2345 /**
2346 * Returns a stream of Packages defined in this class loader
2347 */
2348 Stream<Package> packages() {
2349 return packages.values().stream()
2350 .map(p -> definePackage(p.packageName(), p.module()));
2351 }
2352
2353 // -- Native library access --
2354
2355 /**
2356 * Returns the absolute path name of a native library. The VM invokes this
2357 * method to locate the native libraries that belong to classes loaded with
2358 * this class loader. If this method returns {@code null}, the VM
2359 * searches the library along the path specified as the
2360 * "{@code java.library.path}" property.
2361 *
2362 * @param libname
2363 * The library name
2364 *
2365 * @return The absolute path of the native library
2366 *
2367 * @see System#loadLibrary(String)
2368 * @see System#mapLibraryName(String)
2369 *
2370 * @since 1.2
2371 */
2372 protected String findLibrary(String libname) {
2373 return null;
2374 }
2375
2376 private final NativeLibraries libraries = NativeLibraries.jniNativeLibraries(this);
2377
2378 // Invoked in the java.lang.Runtime class to implement load and loadLibrary.
2379 static NativeLibrary loadLibrary(Class<?> fromClass, File file) {
2380 ClassLoader loader = (fromClass == null) ? null : fromClass.getClassLoader();
2381 NativeLibraries libs = loader != null ? loader.libraries : BootLoader.getNativeLibraries();
2382 NativeLibrary nl = libs.loadLibrary(fromClass, file);
2383 if (nl != null) {
2384 return nl;
2385 }
2386 throw new UnsatisfiedLinkError("Can't load library: " + file);
2387 }
2388 static NativeLibrary loadLibrary(Class<?> fromClass, String name) {
2389 ClassLoader loader = (fromClass == null) ? null : fromClass.getClassLoader();
2390 if (loader == null) {
2391 NativeLibrary nl = BootLoader.getNativeLibraries().loadLibrary(fromClass, name);
2392 if (nl != null) {
2393 return nl;
2394 }
2395 throw new UnsatisfiedLinkError("no " + name +
2396 " in system library path: " + StaticProperty.sunBootLibraryPath());
2397 }
2398
2399 NativeLibraries libs = loader.libraries;
2400 // First load from the file returned from ClassLoader::findLibrary, if found.
2401 String libfilename = loader.findLibrary(name);
2402 if (libfilename != null) {
2403 File libfile = new File(libfilename);
2404 if (!libfile.isAbsolute()) {
2405 throw new UnsatisfiedLinkError(
2406 "ClassLoader.findLibrary failed to return an absolute path: " + libfilename);
2407 }
2408 NativeLibrary nl = libs.loadLibrary(fromClass, libfile);
2409 if (nl != null) {
2410 return nl;
2411 }
2412 throw new UnsatisfiedLinkError("Can't load " + libfilename);
2413 }
2414 // Then load from system library path and java library path
2415 NativeLibrary nl = libs.loadLibrary(fromClass, name);
2416 if (nl != null) {
2417 return nl;
2418 }
2419
2420 // Oops, it failed
2421 throw new UnsatisfiedLinkError("no " + name +
2422 " in java.library.path: " + StaticProperty.javaLibraryPath());
2423 }
2424
2425 /*
2426 * Invoked in the VM class linking code.
2427 */
2428 private static long findNative(ClassLoader loader, String entryName) {
2429 if (loader == null) {
2430 return BootLoader.getNativeLibraries().find(entryName);
2431 } else {
2432 return loader.libraries.find(entryName);
2433 }
2434 }
2435
2436 // -- Assertion management --
2437
2438 final Object assertionLock;
2439
2440 // The default toggle for assertion checking.
2441 // @GuardedBy("assertionLock")
2442 private boolean defaultAssertionStatus = false;
2443
2444 // Maps String packageName to Boolean package default assertion status Note
2445 // that the default package is placed under a null map key. If this field
2446 // is null then we are delegating assertion status queries to the VM, i.e.,
2447 // none of this ClassLoader's assertion status modification methods have
2448 // been invoked.
2449 // @GuardedBy("assertionLock")
2450 private Map<String, Boolean> packageAssertionStatus = null;
2451
2452 // Maps String fullyQualifiedClassName to Boolean assertionStatus If this
2453 // field is null then we are delegating assertion status queries to the VM,
2454 // i.e., none of this ClassLoader's assertion status modification methods
2455 // have been invoked.
2456 // @GuardedBy("assertionLock")
2457 Map<String, Boolean> classAssertionStatus = null;
2458
2459 /**
2460 * Sets the default assertion status for this class loader. This setting
2461 * determines whether classes loaded by this class loader and initialized
2462 * in the future will have assertions enabled or disabled by default.
2463 * This setting may be overridden on a per-package or per-class basis by
2464 * invoking {@link #setPackageAssertionStatus(String, boolean)} or {@link
2465 * #setClassAssertionStatus(String, boolean)}.
2466 *
2467 * @param enabled
2468 * {@code true} if classes loaded by this class loader will
2469 * henceforth have assertions enabled by default, {@code false}
2470 * if they will have assertions disabled by default.
2471 *
2472 * @since 1.4
2473 */
2474 public void setDefaultAssertionStatus(boolean enabled) {
2475 synchronized (assertionLock) {
2476 if (classAssertionStatus == null)
2477 initializeJavaAssertionMaps();
2478
2479 defaultAssertionStatus = enabled;
2480 }
2481 }
2482
2483 /**
2484 * Sets the package default assertion status for the named package. The
2485 * package default assertion status determines the assertion status for
2486 * classes initialized in the future that belong to the named package or
2487 * any of its "subpackages".
2488 *
2489 * <p> A subpackage of a package named p is any package whose name begins
2490 * with "{@code p.}". For example, {@code javax.swing.text} is a
2491 * subpackage of {@code javax.swing}, and both {@code java.util} and
2492 * {@code java.lang.reflect} are subpackages of {@code java}.
2493 *
2494 * <p> In the event that multiple package defaults apply to a given class,
2495 * the package default pertaining to the most specific package takes
2496 * precedence over the others. For example, if {@code javax.lang} and
2497 * {@code javax.lang.reflect} both have package defaults associated with
2498 * them, the latter package default applies to classes in
2499 * {@code javax.lang.reflect}.
2500 *
2501 * <p> Package defaults take precedence over the class loader's default
2502 * assertion status, and may be overridden on a per-class basis by invoking
2503 * {@link #setClassAssertionStatus(String, boolean)}. </p>
2504 *
2505 * @param packageName
2506 * The name of the package whose package default assertion status
2507 * is to be set. A {@code null} value indicates the unnamed
2508 * package that is "current"
2509 * (see section 7.4.2 of
2510 * <cite>The Java™ Language Specification</cite>.)
2511 *
2512 * @param enabled
2513 * {@code true} if classes loaded by this classloader and
2514 * belonging to the named package or any of its subpackages will
2515 * have assertions enabled by default, {@code false} if they will
2516 * have assertions disabled by default.
2517 *
2518 * @since 1.4
2519 */
2520 public void setPackageAssertionStatus(String packageName,
2521 boolean enabled) {
2522 synchronized (assertionLock) {
2523 if (packageAssertionStatus == null)
2524 initializeJavaAssertionMaps();
2525
2526 packageAssertionStatus.put(packageName, enabled);
2527 }
2528 }
2529
2530 /**
2531 * Sets the desired assertion status for the named top-level class in this
2532 * class loader and any nested classes contained therein. This setting
2533 * takes precedence over the class loader's default assertion status, and
2534 * over any applicable per-package default. This method has no effect if
2535 * the named class has already been initialized. (Once a class is
2536 * initialized, its assertion status cannot change.)
2537 *
2538 * <p> If the named class is not a top-level class, this invocation will
2539 * have no effect on the actual assertion status of any class. </p>
2540 *
2541 * @param className
2542 * The fully qualified class name of the top-level class whose
2543 * assertion status is to be set.
2544 *
2545 * @param enabled
2546 * {@code true} if the named class is to have assertions
2547 * enabled when (and if) it is initialized, {@code false} if the
2548 * class is to have assertions disabled.
2549 *
2550 * @since 1.4
2551 */
2552 public void setClassAssertionStatus(String className, boolean enabled) {
2553 synchronized (assertionLock) {
2554 if (classAssertionStatus == null)
2555 initializeJavaAssertionMaps();
2556
2557 classAssertionStatus.put(className, enabled);
2558 }
2559 }
2560
2561 /**
2562 * Sets the default assertion status for this class loader to
2563 * {@code false} and discards any package defaults or class assertion
2564 * status settings associated with the class loader. This method is
2565 * provided so that class loaders can be made to ignore any command line or
2566 * persistent assertion status settings and "start with a clean slate."
2567 *
2568 * @since 1.4
2569 */
2570 public void clearAssertionStatus() {
2571 /*
2572 * Whether or not "Java assertion maps" are initialized, set
2573 * them to empty maps, effectively ignoring any present settings.
2574 */
2575 synchronized (assertionLock) {
2576 classAssertionStatus = new HashMap<>();
2577 packageAssertionStatus = new HashMap<>();
2578 defaultAssertionStatus = false;
2579 }
2580 }
2581
2582 /**
2583 * Returns the assertion status that would be assigned to the specified
2584 * class if it were to be initialized at the time this method is invoked.
2585 * If the named class has had its assertion status set, the most recent
2586 * setting will be returned; otherwise, if any package default assertion
2587 * status pertains to this class, the most recent setting for the most
2588 * specific pertinent package default assertion status is returned;
2589 * otherwise, this class loader's default assertion status is returned.
2590 * </p>
2591 *
2592 * @param className
2593 * The fully qualified class name of the class whose desired
2594 * assertion status is being queried.
2595 *
2596 * @return The desired assertion status of the specified class.
2597 *
2598 * @see #setClassAssertionStatus(String, boolean)
2599 * @see #setPackageAssertionStatus(String, boolean)
2600 * @see #setDefaultAssertionStatus(boolean)
2601 *
2602 * @since 1.4
2603 */
2604 boolean desiredAssertionStatus(String className) {
2605 synchronized (assertionLock) {
2606 // assert classAssertionStatus != null;
2607 // assert packageAssertionStatus != null;
2608
2609 // Check for a class entry
2610 Boolean result = classAssertionStatus.get(className);
2611 if (result != null)
2612 return result.booleanValue();
2613
2614 // Check for most specific package entry
2615 int dotIndex = className.lastIndexOf('.');
2616 if (dotIndex < 0) { // default package
2617 result = packageAssertionStatus.get(null);
2618 if (result != null)
2619 return result.booleanValue();
2620 }
2621 while(dotIndex > 0) {
2622 className = className.substring(0, dotIndex);
2623 result = packageAssertionStatus.get(className);
2624 if (result != null)
2625 return result.booleanValue();
2626 dotIndex = className.lastIndexOf('.', dotIndex-1);
2627 }
2628
2629 // Return the classloader default
2630 return defaultAssertionStatus;
2631 }
2632 }
2633
2634 // Set up the assertions with information provided by the VM.
2635 // Note: Should only be called inside a synchronized block
2636 private void initializeJavaAssertionMaps() {
2637 // assert Thread.holdsLock(assertionLock);
2638
2639 classAssertionStatus = new HashMap<>();
2640 packageAssertionStatus = new HashMap<>();
2641 AssertionStatusDirectives directives = retrieveDirectives();
2642
2643 for(int i = 0; i < directives.classes.length; i++)
2644 classAssertionStatus.put(directives.classes[i],
2645 directives.classEnabled[i]);
2646
2647 for(int i = 0; i < directives.packages.length; i++)
2648 packageAssertionStatus.put(directives.packages[i],
2649 directives.packageEnabled[i]);
2650
2651 defaultAssertionStatus = directives.deflt;
2652 }
2653
2654 // Retrieves the assertion directives from the VM.
2655 private static native AssertionStatusDirectives retrieveDirectives();
2656
2657
2658 // -- Misc --
2659
2660 /**
2661 * Returns the ConcurrentHashMap used as a storage for ClassLoaderValue(s)
2662 * associated with this ClassLoader, creating it if it doesn't already exist.
2663 */
2664 ConcurrentHashMap<?, ?> createOrGetClassLoaderValueMap() {
2665 ConcurrentHashMap<?, ?> map = classLoaderValueMap;
2666 if (map == null) {
2667 map = new ConcurrentHashMap<>();
2668 boolean set = trySetObjectField("classLoaderValueMap", map);
2669 if (!set) {
2670 // beaten by someone else
2671 map = classLoaderValueMap;
2672 }
2673 }
2674 return map;
2675 }
2676
2677 // the storage for ClassLoaderValue(s) associated with this ClassLoader
2678 private volatile ConcurrentHashMap<?, ?> classLoaderValueMap;
2679
2680 /**
2681 * Attempts to atomically set a volatile field in this object. Returns
2682 * {@code true} if not beaten by another thread. Avoids the use of
2683 * AtomicReferenceFieldUpdater in this class.
2684 */
2685 private boolean trySetObjectField(String name, Object obj) {
2686 Unsafe unsafe = Unsafe.getUnsafe();
2687 Class<?> k = ClassLoader.class;
2688 long offset;
2689 offset = unsafe.objectFieldOffset(k, name);
2690 return unsafe.compareAndSetReference(this, offset, null, obj);
2691 }
2692 }
2693
2694 /*
2695 * A utility class that will enumerate over an array of enumerations.
2696 */
2697 final class CompoundEnumeration<E> implements Enumeration<E> {
2698 private final Enumeration<E>[] enums;
2699 private int index;
2700
2701 public CompoundEnumeration(Enumeration<E>[] enums) {
2702 this.enums = enums;
2703 }
2704
2705 private boolean next() {
2706 while (index < enums.length) {
2707 if (enums[index] != null && enums[index].hasMoreElements()) {
2708 return true;
2709 }
2710 index++;
2711 }
2712 return false;
2713 }
2714
2715 public boolean hasMoreElements() {
2716 return next();
2717 }
2718
2719 public E nextElement() {
2720 if (!next()) {
2721 throw new NoSuchElementException();
2722 }
2723 return enums[index].nextElement();
2724 }
2725 }